Fracture-healing is a specialized type of woundhealing response in which the regeneration of bone leads to a restoration of skeletal integrity. While the process of fracture-healing is usually considered to be biologically optimum. the healing of 5 to 10 pen cent of the estimated 5.6 million fractures occurring annually in the United States is delayed or impaired”. The cause of the impaired healing is often unknown. However, problems with operative and non-operative interventions. such as inadequate mobilization of the fracture, distraction of fracture fragments by fixation devices or traction, repeated manipulations or excessive early motion of a fracture, or excessive peniosteal stripping and damage to other soft tissues during operative exposure, intenfene with healing and may cause a delayed union or a non-union. A delayed union on a non-union may also occur if a fracture becomes contaminated at the time of the injury or after an operation or if an acceptable apposition of the fracture fragments on stable fixation is not achieved25. Moreover. specific pants of the skeleton, such as the neck of the talus. the neck of the femur, and the campal scaphoid5, are known to be at increased risk for impaired fracture-healing. and there may be problems related to peculiarities of the local blood supply or difficulties with the control of the mechanical strain environment at these sites. Thus. while most fractures heal without problems. there are several conditions unden which enhancement of the repair process would be of great benefit to ensure the rapid restoration of skeletal function. The ability of injured patients to return to the work force or to recreational activities early would not only have a substantial economic impact on society but would also improve the oven-all physical and mental well-being of the patients. In this article, I will review some of the better descnibed and more extensively tested methods that have been used to stimulate fracture-healing. I will also provide an introduction to certain new technologies that could improve the repair of fractures. The article is organized in two sections. The first section is a discussion

Enhancement of fracture-healing.

Fifty patients with inadequate bone volume for implant placement were treated with mandibular bone grafts from the symphysis or ramus. The choice of donor site was determined by defect morphology and recipient site location. Although the harvest of bone was associated with low morbidity, the ramus donor site resulted in fewer complications. Implants were placed secondarily following a 4- to 6-month healing period. The onlay grafts exhibited minimal resorption and maintained their dense quality. The symphysis grafts were larger in overall volume, with a corticocancellous morphology. The ramus area provided essentially a cortical graft that was well suited for veneering ridge deficiencies; however, the surgical access in some cases was more difficult than in the anterior mandible.

https://coimplante.odo.br/Biblioteca/Enxertos/Comparison%20of%20Intraoral%20Donor%20Sites%20for%20Onlay%20Grafting%20-%20Craig%20Misch.pdf

Comparison of intraoral donor sites for onlay grafting prior to implant placement.

A group of 15 partially edentulous patients who needed alveolar ridge augmentation for implant placement, were consecutively treated using a two-stage technique in an outpatient environment. A total of 18 alveolar segments were grafted. During the first operation bone blocks harvested from the mandibular ramus or symphysis were placed as lateral or vertical onlay grafts and fixed with titanium osteosynthesis screws after exposure of the deficient alveolar ridge. After 6 months of healing the flap was re-opened, the screws were removed and the implants placed. Twelve months after the first operation implant-supported fixed bridges could be provided to the patients. Mean lateral augmentation obtained at the time of bone grafting was 6.5±0.33 mm, that reduced during healing because of graft resorption to a mean of 5.0±0.23 mm. Mean vertical augmentation obtained in the 9 sites where it was needed was 3.4±0.66 mm at bone grafting and 2.2±0.66 mm at implant placement. Mean lateral and vertical augmentation decreased by 23.5% and 42%, respectively, during bone graft healing (before implant insertion). Mandibular sites showed a larger amount of bone graft resorption than maxillary sites. All the 40 implants placed were integrated at the abutment connection and after prosthetic loading (mean follow-up was 12 months). No major complications were recorded at donor or recipient sites. Soft tissue healing was uneventful, and pain and swelling were comparable to usual dentoalveolar procedures. A visible ecchymosis was present for 4 to 7 days when the bone was harvested from the mandibular symphysis. From a clinical point of view this procedure appears to be simple, safe and effective for treating localised alveolar ridge defects in partially edentulous patients.

Clinical results of alveolar ridge augmentation with mandibular block bone grafts in partially edentulous patients prior to implant placement

This study examined the influence of controlled occlusal overload on an implant. An experiment was conducted on five crab-eating monkeys (Macaca fascicularis) in which overload with no inflammation in the peri-implant tissues was modeled. Two osseointegrated implants were placed into each monkey. After 3 months of osseointegration, superstructures that were excessive by about 100 microns were mounted on the implants, and a traumatic occlusal force was experimentally delivered to its implant from the lingual to the buccal side. This procedure was performed under conditions of good oral hygiene. The monkeys received an excessive occlusal force for 1 to 4 weeks and were then immediately sacrificed. The results showed that the implants remained firmly integrated with bone, and all of the subjects that received excessive occlusal force for 1 to 4 weeks showed an absence of gross bone loss. These results suggest that conditions of occlusal force created by excessively high implant-supported superstructures may not destroy the peri-implant tissues.

The influence of controlled occlusal overload on peri-implant tissue. part 4: a histologic study in monkeys.

The superior volume maintenance of membranous over endochondral bone has been shown in several studies and provides the basis for its preferred clinical use as an onlay grafting material in the craniofacial skeleton. The scientific rationale for this seeming embryologic advantage, however, has never been proven. Our hypothesis is that the pattern of onlay bone graft resorption is primarily determined by a graft's micro-architecture (relative cortical and cancellous composition) rather than its embryologic origin (membranous versus endochondral). Twenty-five adult New Zealand, White rabbits were used for this study. Eight animals were killed at 3 weeks, eight animals at 8 weeks, and nine animals at 16 weeks. Three graft types were placed onto each rabbit cranium: cortical bone graft of membranous origin and cortical and cancellous bone graft of endochondral origin. Fluorochrome markers were injected into all living rabbits at 1, 6, and 14 weeks. Microcomputed tomography scanning was performed on all of the bone grafts to determine postsacrifice volumes and to obtain detailed information regarding the bone graft's trabecular architecture. In addition, specimens were examined histologically. Volume analysis showed a statistically greater resorption rate in the cancellous endochondral bone graft than in either the endochondral or membranous cortical bone grafts (p < 0.05) for all time points. In addition there was no significant difference in the resorption rates between the endochondral and membranous cortical bone grafts. A post-test power analysis (alpha = 5 percent) of the volume data comparing the two types of cortical bone grafts showed that a difference in resorption of 8.9 percent would be detected with a 90-percent probability. Previous studies, which have shown a seeming superiority of membranous over endochondral bone grafts, used composite grafts composed of both cortical and cancellous portions. By separating these components, we have shown that cortical bone grafts maintain their volumes significantly better than cancellous bone grafts. In addition, we found no statistical difference in the resorption rates between the two cortical onlay bone grafts of different embryologic origins, a finding that has never been previously published. From our results, we believe cortical bone to be a superior onlay grafting material, independent of its embryologic origin. We believe these results challenge the currently accepted theories of bone graft dynamics and may lead to a change in the way clinicians approach bone graft selections for craniofacial surgery.

Volume maintenance of onlay bone grafts in the craniofacial skeleton : Micro-architecture versus embryologic origin

This paper investigates the relationship between bone resorption, the process of bone revascularization, and graft fixation. Vital staining techniques and microangiography were used to study the extent of graft revascularization of fixed and nonfixed endochondral (rib) and membranous (skull) onlay b

John H. Phillips

Papers

Fixation effects on membranous and endochondral onlay bone graft revascularization and bone deposition.